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Pete
Pete, Cadillac Technician
Category: Cadillac
Satisfied Customers: 24704
Experience:  17 years Cadillac experience as a technician.
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I have a 2007 Cadillac in my shop 2 weeks trying to figure

Customer Question

Hi I have a 2007 Cadillac in my shop for over 2 weeks trying to figure out why it will not start when warmed up. It cranks and cranks but will not start. I have replaced the fuel pump and have 57 to 59 psi at fuel rail not running and the same when running. it also starts very hard cold. runs rough then comes into it. could leave running all day and not miss a beat but shut it off and will not restart thanks Dave
Submitted: 1 year ago.
Category: Cadillac
Customer: replied 1 year ago.
no codes
Expert:  Eric replied 1 year ago.

HI,

I am sorry that you have not been helped yet. I just came online and saw your question

How long does it hold pressure with key on engine off, and key off?

Is the spark bright blue when it is hard to start or wont start?

What is the rpm cranking signal look like on the no start?

Please remember that I am not there to test anything and rely on you for as much detail as possible

Customer: replied 1 year ago.
It starts cold but hard and the pressure is @58 then when hot it does not start at all and the fuel pressure is at 47 not higher . I put a new gm delco fuel pump in it.
Customer: replied 1 year ago.
It will start hot with insint start immediately
Customer: replied 1 year ago.
Runs dont understand what is going on!
Expert:  Eric replied 1 year ago.

HI,

did you replace the whole fuel pump module or just the pump motor itself

Customer: replied 1 year ago.
whole pump module with factory pump
Expert:  Eric replied 1 year ago.

HI,

Sounds like it is a defective pump but I will opt out and see if another expert has any other ideas

Expert:  Mike S. replied 1 year ago.

If this problem was there before the new fuel pump, I doubt if that is it. If it was there before and the new pump didn't help and there are no codes and also it starts with starting fluid " insint start", I assume that is what that meant, then perhaps the fuel injector pulse is just off somewhat and the engine is flooding. I would reprogram the ecm/pcm with the latest software and try that.

Customer: replied 1 year ago.
I had the e m reprogrammed at the Cadillac dealership and it didn't change anything thanks Dave
Customer: replied 1 year ago.
Ecm
Expert:  Mike S. replied 1 year ago.

Well, that was my 2 cents worth. You should have mentioned that but anyhow, I will opt out now, too. Maybe another expert has something eels to add.

Expert:  Pete replied 1 year ago.

Hi my name is ***** ***** I will be happy to assist with this today.In some cases I may need more info to assist better.I apologize for any delay.

Do you smell fuel at all when this hard start occurs when the engine is hot or cold on the inside or outside of the vehicle especially at the exhaust?

Let me know so we can continue,thanks Pete.

Customer: replied 1 year ago.
Thanks no fuel smell and will start cold . I cycle the key 3 times and it starts. Fuel pressure is at 59.when hot it will not start and pressure is at 47 key on
Expert:  Pete replied 1 year ago.

When the fuel pump was replaced did you check the fuel pump connection for any corrosion at any of the terminals or damaged/corroded wiring at the connection?

Customer: replied 1 year ago.
it seemed fine. No corrosion
Expert:  Pete replied 1 year ago.

O.k.,you shouldnt see the pressure drop below 50 psi so the low (47 psi) of pressure is causing this here.Since the pump is new and this was also an issue with the old pump pressure the pump isnt the cause here.

I suspect you have a low voltage or ground issue to the pump when it heats up causing the low pressure issue.This is most common with poor connections at the pump itself or a fault with the ground that feeds the pump.The ground for the pump comes in on the black wire in terminal A at the pump.This black wire connects to ground G300.

G300 is located on the frame rail near the fuel tank as seen here.Make sure it is clean and tight and remove it and clean the area.Clean the battery ground as well as where the ground leads to from the battery to see if this corrects this issue here.

https://www.dropbox.com/s/6tpumw0gb6ica4g/g300-12-07.gif?dl=0

If more help is needed, use the reply tab to continue our conversation. If no further assistance is needed, kindly rate my service.You can rate at any time and we can continue to work on your question as this will not close out your question.Keep in mind in some cases it can be difficult to fully diagnose or help repair your vehicle without seeing it and I work on delivering the best possible answer from what I see to work with.

Thanks Pete